Well it is not just him. Ask the average person on the street what the best offroader is and depending if you ask a redneck or a regular person I would bet 90%of them would either say a Z71 or a Jeep. The Z71 because the some people that own them think that a sticker package makes them invincible (atleast thats what the comment on my offroading videos and my little brother makes me think), and the Jeep because most likely everyone has a grandfather/uncle/cousin that owned one and talked it up plus Jeep has done some very good marketing. outside of some of the Toyota trail team ads in off road magazines I really cant think of any bragging toyota has done on their offroad ability.
It is like people with low self esteem say: if you hear something enough you start to believe it. Jeep has just said it enough that people believe it alot.